1. Field of the Invention
This invention relates to a novel isoindoline derivative which is a superior synthetic antibacterial substance and to a process for its preparation.
2. Description of the Background
A number of pyridonecarboxylic acid derivatives as synthetic antibacterial materials have been synthesized in recent years. These include norfloxacin (Japanese Patent Laid-open No.141286/1978), enoxacin (Japanese Patent Laid-open No.31042/1980), ofloxacin (Japanese Patent Laid-open No.46986/1982), ciprofloxacin (Japanese Patent Laid-open No. 74667/1983), and the like. A feature common to these compounds is that they have a quinoline structure or a naphthyridine structure, both having a fluorine atom substituted at 6 position and a secondary amino group at 7 position. In particular, introducing a piperazine group or a pyrrolidine group to the 7 position of a quinoline or a naphthyridine structure is considered to effect enhanced antibacterial activitites. These compounds, however, are considered not to be complete in their effects of antibacterial activity, absorptivity through enteric canal, and metabolic stability. In addition, their side effects have been a problem.
The present inventors have undertaken extensive studies in order to develop an antimicrobial substance having a superior effects without the problem of side effects and useful for clinical purposes. As a result, the inventors have found that compounds having an isoindoline ring at 7 position of a quinoline or naphthyridine structure show extremely strong antibacterial activity not only against gram negative microorganisms but also against gram positive microorganisms. This finding has led to the completion of this invention.